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 A270913 Coefficient of x^n in Product_{k>=1} (1+x^k)^n. 21
 1, 1, 3, 13, 51, 206, 855, 3585, 15155, 64525, 276278, 1188353, 5130999, 22226049, 96544003, 420368858, 1834203955, 8018057345, 35107961175, 153950675585, 675978772326, 2971700764941, 13078268135683, 57613905606273, 254038914924791, 1121081799217231 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 LINKS Vaclav Kotesovec, Table of n, a(n) for n = 0..1000 FORMULA a(n) ~ c * d^n / sqrt(n), where d = A270914 = 4.5024767476173544877385939327007... and c = A327280 = 0.260542233142438469433860832160... MATHEMATICA Table[SeriesCoefficient[Product[(1+x^k)^n, {k, 1, n}], {x, 0, n}], {n, 0, 25}] Table[SeriesCoefficient[QPochhammer[-1, x]^n, {x, 0, n}]/2^n, {n, 0, 25}] Table[SeriesCoefficient[Exp[n*Sum[(-1)^j*x^j/(j*(x^j - 1)), {j, 1, n}]], {x, 0, n}], {n, 0, 25}] (* Vaclav Kotesovec, May 19 2018 *) PROG (PARI) {a(n)=polcoeff(prod(k=1, n, (1 + x^k +x*O(x^n))^n), n)} for(n=0, 20, print1(a(n), ", ")) \\ Vaclav Kotesovec, Aug 26 2019 CROSSREFS Cf. A008485, A255526, A270914, A270917, A270919. Sequence in context: A197074 A014985 A015521 * A323266 A146279 A098619 Adjacent sequences:  A270910 A270911 A270912 * A270914 A270915 A270916 KEYWORD nonn AUTHOR Vaclav Kotesovec, Mar 25 2016 STATUS approved

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Last modified October 18 10:59 EDT 2019. Contains 328147 sequences. (Running on oeis4.)